It is previously known, as by patents DE 42 19253 and DE 43 43650, to make handles for screwdrivers or similar tools from several materials with different hardness. A hard material is then chosen as an inner core to ensure a safe transmission of force and torque to the metal shaft of the tool, and a soft material with high friction is preferred for the outer layer in contact with the hand. The parts from different materials can either be separately manufactured and joined in a second step as in DE 43 43650, or cast together in a two step injection moulding as in DE 42 19253.
To aim and use the tool with precision, the hand must feel the resistance from the workpiece against the metal tip of the tool. This requires that the soft material has small thickness and a suitable surface structure. The boundary surface between the materials is then a critical area, which must be made with ribs or indentations to withstand force and torque, since the deformation properties for soft and hard materials are so different, that the soft layer would otherwise easily crumple and loosen, especially if the layer is thin.
The invention concerns a handle with a handgrip structure combining the high friction of a soft material, a surface structure and small thickness allowing accurate feeling of the workpiece resistance and a hard inner core with high strength.